Messages in this thread | | | Date | Thu, 26 Jul 2012 10:30:09 -0400 | Subject | Question about the fallocate system call | From | Jidong Xiao <> |
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Hi,
I just have a simple question about fallocate.
I want to test the punch hole function of fallocate(). So I wrote such a simple program:
yosemite:/mnt # cat test.c #include <fcntl.h> #include <errno.h> #include <stdio.h> #include <stdint.h> #include <linux/fs.h> #include <linux/falloc.h>
int main(void) { int fd;
fd = open("testfile", O_RDWR); fallocate(fd,FALLOC_FL_PUNCH_HOLE,0,500*1024*1024); close(fd);
return 0; }
I created a file called "testfile" whose size is 1GB, however, when I run the above program, the size of the testfile simply won't change, if I use stat command to check the file status, nothing is changed when I execute the above program. My filesystem is ext4, as I understand, ideally when I run the above program, the file size should decrease from 1GB to 512MB, is there anything wrong with the program or I just understood incorrectly?
Thank you for any inputs/comments.
-Jidong
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